Xanthine derivatives such as theophylline and .beta..sub.2 agents such as salbutamol have been known as drugs having a relaxing action to tracheal smooth muscles.
However, in those drugs which have been already known, their relaxing action of tracheal smooth muscles in airway diseases and pulmonary diseases such as bronchial asthma, acute and chronic bronchitis, pulmonary emphysema and upper esophagitis is not satisfactory in terms of a balance with the side effect.
In view of the above, an object of the present invention is to offer drugs having novel relaxing action to tracheal smooth muscle exhibiting far better action to airway diseases, etc.